Digital microfluidics is an alternative paradigm for lab-on-a-chip systems based upon micromanipulation of discrete droplets. Microfluidic processing is performed on unit-sized packets of fluid which are transported, stored, mixed, reacted, or analyzed in a discrete manner using a standard set of basic instructions. In analogy to digital microelectronics, these basic instructions can be combined and reused within heirarchical design structures so that complex procedures (e.g. chemical synthesis or biological assays) can be built up step-by-step. And in contrast to continuous-flow microfluidics, digital microfluidics works much the same way as traditional bench-top protocols, only with much smaller volumes and much higher automation. Thus a wide range of established chemistries and protocols can be seamlessly transferred to a nanoliter droplet format.
Research in Dr. Richard Fair's laboratory at Duke University has focused on the use of electrowetting arrays to demonstrate the digital microfluidic concept. Electrowetting is essentially the phenomenon whereby an electric field can modify the wetting behavior of a droplet in contact with an insulated electrode. If an electric field is applied non-uniformly then a surface energy gradient is created which can be used to manipulate a droplet sandwiched between two plates. Electrowetting arrays allow large numbers of droplets to be independently manipulated under direct electrical control without the use of pumps, valves or even fixed channels.
Andrew C. Madison, Matthew W. Royal, Frederic Vigneault, Liji Chen, Peter B. Griffin, Mark Horowitz, George M. Church, and Richard B. Fair, "Scalable device for automated microbial electroporeation in a digital microfluidic platform," ACS Synthetic Biology vol.6, pp.1701-1709 PDF
R.B. Fair, "Demonstration of Automated Analysis of Multiple Analytes on an Integrated Digital Microfluidic Platform," Clinical Chem. March 15,2017 PDF
J.A. Moore, N. Nemat-Gorgani, A.C. Madison, M.A. Sandahl, S. Punnamaraju, A.E. Eckhardt, M.G. Pollack, F.M Vigneault, G.M. Church, R.B. Fair, M.A. Horowitz and P.B. Griffin, "Automated electrotransformation of E. Coli on a digital microfluidic platform using bioactivated magnetic beads." Biomicrofluidics, vol.11, p.014110 PDF
A.C. Madison, M.W. Royal, and R.B. Fair "Fluid transport in partially shielded electrowetting on dielectric digital microfluidic device" J. Microelectromechanical Sys., vol.25, 593-605 PDF
L. Chen and R.B. Fair "Digital microfluidics chip with integrated intra-droplet magnetic bead manipulation" Microfluid Nanofluid, published online 24 September, 2015, Print: vol.19, No.6, pp.1335-1348, Dec,2015 PDF
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Chip mixes droplets faster, MIT Technology Review, October 2003.
Chip Juggles Droplets, Technology Research News, Sep. 4-11, 2002.
Digital Microfluidics, Slashdot, August 3, 2002.
Laboratory on a Chip, Popular Mechanics, March 2002.
Lab-on-a-Chip Technology May Present New ESD Challenges, Electrostatic Discharge Journal, March 2002.
Making Materials Fit the Future, R&D Magazine, December 2001.
Email: rfair AT ee.duke.edu
Department of Electrical and Computer Engineering
Durham, NC 27708